Invisible Soldier

20

Complete the REVOLUTION level without killing and raising an alarm.

After jumping out of the vent, you are not to be found by any enemy or kill anyone. If you are found, you may reload a checkpoint. This does not affect the achievement. Be sure to pay attention to your blue light on your watch. If this light is on, you will be seen by enemies.

Revolution is one of the longest levels in the game, as well as having the most enemies. Take your time and sneak around all enemies. Turn off all lights when available, and knock out enemies whenever possible.

Just so everyone knows, if you kill someone or activate an alarm, you can still get the achievement by loading the last checkpoint (before dying or reaching another checkpoint of course). At the moment i've only tested it for this level, but I imagine it's the same for every mission where you can't kill or raise an alarm.